1. Technical Field
This invention is in the field of liquid handling, and more specifically is in the field of disposable capillary pipet devices for picking up and transferring a selected volume of liquid such as blood from one point to another for testing.
2. Background of the Prior Art
Capillary pipet devices are known for transferring liquids such as a specimen of blood from a patient to a test tube or testing apparatus. A drop of blood is produced by sticking the finger of a patient with a needle, the blood is picked up by a pipet and is taken to a machine where the blood is tested and analyzed. Capillary tubes are excellent for drawing blood from this drop because the capillary tubes suck the blood up into the tubes at a speed that does not also draw up air bubbles, which are undesireable.
However, a problem arises in trying to eject the blood from the capillary tube. It is conventional to provide a rubber bulb that fits over the vent end of the capillary tube, which is away from the liquid intake and emission end. To eject the liquid from the tube, the operator places a finger over a hole in the top of the bulb and squeezes the bulb to force air against the liquid and push the liquid out of the tube. However, the liquid bubbles at the end and the last drop of liquid is always hard to get out. It may be possible to get the last drop out of the tube by shaking but this is messy and the last drop may not go where desired. In any event, prior methods do not deliver a precise volume of blood to a testing machine, and without a precise volume of blood the testing machine cannot perform its tests accurately.